Intercellular signaling is essential for complex microbial events such as development, pathogenesis and biofilm formation. Myxococcus xanthus is an excellent model bacterium for studying intercellular signaling because of its complex life cycle and coordinated social behaviors. This study focuses on M. xanthus social gliding motility and chemotaxis, a multi-cellular function involved in vegetative swarming and fruiting body formation. Previous studies show that social gliding motility/chemotaxis of M. xanthus involves the complex interactions of three major cellular components: type IV pili (TFP), exopolysacchrides (EPS), and a chemotaxis-like Frz sensory system (Frz). This study aims to understand the genetic and biochemical basis of M. xanthus social gliding motility/chemotaxis. Three specific aims are proposed in this application. Aim 1 is to analyze the genetic and biochemical properties of PilA to further understand the role of TFP in S-motility. Aim 2 is to study the molecular mechanisms associated with temporal and spatial control of EPS production and distribution to further understand the role of EPS in S-motility. Aim 3 is to explore the interaction between TFP &EPS and its associated biological events. The successful execution of these proposed studies will provide a molecular understanding of the TFP-EPS-Frz-associated social gliding motility and chemotaxis. The findings will reveal insightful biological knowledge about intercellular signaling events during the complex development of M. xanthus. Furthermore, these studies could discover the possible evolutionary connections between flagella based swimming motility and TFP dependent gliding motility. Since TFP, EPS and chemosensory proteins are also the key virulent factors for a variety of pathogenic bacteria during biofilm formation and tissue adherence and invasion, the knowledge gained from this study could also lead to new ways to combat microbial pathogenesis.